This invention relates generally as indicated to an aircraft fuel booster pump assembly with altitude start capabilities, and more particularly to a fuel tank booster or standby pump which can readily be started over a wide range of altitudes and temperatures to establish and maintain rated flow at specified outlet pressure.
Jet fuel is usually supplied to the engines of the aircraft by an engine driven pump. However, because the fuel tanks are usually low relative to the engine, a tank pump is also normally required to pump the fuel to the engine under pressure to prevent cavitation in the engine driven pump and to minimize wear and improve the efficiency thereof.
In such aircraft fuel systems, for flight safety reasons, redundant or standby pumps are also required so that in the event of a failure of the main fuel tank pump, or a drop-off in pressure, the booster pump can still provide sufficient fuel line pressure to effect movement of the fuel from tank-to-tank and from tank to the engine.
Ideally such booster pumps should preferably be off except when needed to maintain the desired fuel line pressure. However, in actual practice it has been found that if the usual aircraft fuel booster pumps are required to be started at high altitudes, they may fail to prime themselves and not effect the required movement of the fuel. To avoid this problem, the normal practice has been to start the booster pumps during ground operations and keep the pumps operating during the entire flight or until the fuel is exhausted from the particular tanks in which the booster pumps are located. Since the actual fuel flow requirements of systems with redundant or standby pumps are only a fraction of the total system capability when all systems are working, operating redundant fuel pumps during the entire flight results in wasted consumption of electrical power, and in many cases taxes the aircraft electrical generating systems to their limits. The entire operation also results in a reduction of fuel available for the engines and a reduction in flight range for the aircraft.